In various mechanical devices fluid pressure such as pneumatic or hydraulic pressure is used as a motive force to operate various components of the mechanism. For example, in an apparatus for attaching fasteners such as pronged buttons to a fabric article, such as the apparatus disclosed in U.S. Pat. Nos. 3,964,661 and 3,987,950, a pneumatic cylinder is used to assemble two components of the fastener element on to a fabric article. The pressure supplied by the cylinder is critical in assembling the two portions of the fastener together in that if too low of a pressure is utilized, the parts will not be completely assembled and thus will be more subject to failure. If too high of a pressure is utilized then the parts will be subject to damage.
It is necessary during the operation of the apparatus, however, to adjust the pressure of the cylinder as needed in order to compensate for various factors encountered in the manufacturing process. On commercially available devices, a pressure regulator is provided in which there is an adjustment mechanism, generally in the form of a threaded member which can be moved axially within the pressure regulator body to provide the necessary adjustment. However operators may inadvertently select a pressure which is below a necessary minimum pressure to achieve an adequate assembly of the parts. Therefore, it would be advantageous if there were provided a pressure regulator which could be pre-set to provide a minimum pressure and which could be adjustable to provide a preselected range of pressures above the pre-set minimum pressure.
Another feature of pressure regulators generally is to have a vent or bleed hole which is necessary to prevent an excessive amount of pressure and to accurately maintain the pressure selected through adjustment of the pressure regulator. Again, operators may inadvertently or purposefully block the vent hole to cause the apparatus, in some instances, to operate faster, but in any event, to subvert the functioning of the pressure regulator. Therefore, it would be an improvement to the art to assure proper venting of the pressure regulator while avoiding inadvertent or purposeful blocking.